Safety fuse device



Sept. 22, 1931. J. STONE 1,824,415

SAFETY FUSE DEVICE Filed Sept. 9, 1929 JESSE S1035; I N VEN TOR.

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A TTORNEX Patented Sept. 22, 1931 UNITED STATES PATENT ori-ICE JESSEs'roNE, Yor PITTSBURGH, PENNSYLVANIA SAFETY FUSE DEvIcE .ApplicationfledSeptember 9, 1929. Serial No. 391,450.

the improvements which will be herein more 1U fully described may beyused with the ordinary fuse blocks now in use, while at the same timethe fuse plugs now in use may not be used with any fuse blocks to whichmy improvements have been applied. In order to use'any fuse block havingmy inventionadded thereto, a special type of fuse plug is required-,'thenature of Vwhich will also be fully described in this specifica--c-tion. The adaptability of myinvention for use without changing ofarts, in connection with the ordinary type ofpfuseblocks in common use,will readily be understood from the description, and it will be at onceseen that this feature constitutes ajvery desirablev one,

in my invention.

Two important features of the present in- Vention are the following, towit, the modification of the bottom end of an ordinary 4F In thedrawingsforming part of the present specification, l y

Figure 1 is a sectional view of my invention mounted -in a fuse block,and taken on line 1-1 of Figure 2. 50

Figure 2 is a plan View ofjthefuse block fuse plug,b the addition of acontact pin shown in Figure 1, the fuse plug and the Spe cial washer,'or adapter being omitted for f clearness of illustration.

Figure 3 is a vertical partial section of the base of the fuse plug, andthe adapter with associated parts.

Figure 4 is a top plan view of the fuse plug.

Figure 5 is a bottom view of the fuse plug.

Figure 6 is a plan View' of the special washer or adapter.

Figure 7 is a side view of Figure 6.

Figure 8 is a plan View of a locking spring ring used in connection withthe adapter.

Figure 9 is a side view of the ring shown in Figure 8. e

In the drawings, the numeral 1, indicates a porcelain base, called thefuse block, of the form shown, provided with the usual necessary parts,such as the ingoing or feeder connection 2, and the outgoing branchcircuit connection 3, the cup-shaped recess 4, with a metal ferrule 5seated therein. The connection 2, leads by means of the bent plate 6 tothe contact pin 7, shown clearly in Figure 1. f

The connection 3 is provided with a yoke 8, which is accommodated withinthe ferrule 5, and lies on the bottom 9 thereof. Above the yoke is aninsulating thin washer 10, and a metal holding washer 11, and it is seenthat the contact screw 7 passes through the cluster of parts just named,and down through the porcelain fuse yblock to the bent plate 6,'and issecured thereto, in the usual fashion. It will be noted the head 12 ofthe contact screw 7 is iattened somewhat, so that itseats nicely in thebottom recess 13 of the special micarta washer 14, see Figure 3.

The special washer, 14, or adapter ismade preferably of a hard,non-conductive, material such as compounded substances like micarta,which is composed of mica and other substances, commonly used in thetrade. The purpose of requiring substantially hard material, will bemore fully described below.

The cross-sectional shape or form of the adapter 14 is shown in Figure3, and a plan view in Figure 6, in which it is seen that a concentricrecess 15 is formed in the top of same, and a perforation 16 passesthrough the center, adapted to receive the fuse plug Vcontact pin 17.VOn the bottom Vof the wire in a compressed-position within the`periphery of the adapter, Vas shown in Figure 7. It will be seenV thatwhile the spring .wire 19` is in 'compressed position, that the adaptercan be inserted freely within the ferrule l5,Y and placed at the bottomthereof,

v on top of the head 12, of the contact screw 7,

with the former in the recess 13. Vhen the adapter is in this positionthe pin 2O is withdrawn, and the wire 19'springs outward, and locksitself in the grooves 23 of the ferrule 5, and the adapter then cannotbe removed without destroying ferrule 5. The purpose of this is toenable theordinary ferrule of theV fuse block to be used with my`inventiomwithout anychanges being made. It is evident that this is avery importantfeature of the device, in that the present fuse blocks canbe used without changes in their construction. Y

The fuse plug base, whichis newly formed in' the present invention,consists of the following. VThe portion of the fuse' plug 24, which isabove the corrugated pro3ecting disc 25, is substantially the same as incommon use, `except that the length of the plug is shortened. Mounted onthe plug 24, is the fuse plug disc 25, which is formed preferably of thesame material as the adapter, to wit, of a hard, insulating pressedsubstance, or com-v pound, which'has been made under hydraulic.r

or other great pressure. On the face-.of the disc 25, is mounted aconcentric proJecting ringl 26, preferably made integral therewithand-also formed'complementary inshape with the recess 15 of the adapterbefore described, so it is evidentithe fuse plug base fits snugly intolthe upper face of the adapter, and 'the I contact pin passesthrough thecenter perforation 16 yof the latter and makes contact with the top 12of the contact screw 7, when the fuse plug 24 is screwed home7 in thethreads of the ferrule-5. 4The contact pin may be mounted in anysuitable rigid manner to the upper portion of the fuse plug 24, andthe`latter has the usual fusible element 27 within.

it for carrying the current from the cont-act pin-to the fuse 28, whichin turn leads same to the metal screw threadscovering the plugrat' l 30,which in turn contact the threads 'of the This pinis only for atemporary Apin 17 will not, due to the thickness of the wire ferrule 5.From ferrule 5 it reaches the yoke 8 and the branch circuit connection3.

From what has been said it is seen that electric current comes inthrough the feederconnection 2, passes through bent plate 6, intocontact screw 7. Then to the contact pin 17, and through the parts justdescribed above to the branch circuit connection 3.

Vx.lVith reference to the surreptitious use of the device, it is quiteevident that coins cannot be used in any manner to form a connectionelectrically between the head 12 of the contactscrew 7, and walls of theferrule 5, which is necessary in order to close the circuit fromconnections 2 to 3. Y 1 Y A i' v Should a piece of wire be wrappedaround the contact pin 17 of the fuse plug, insuchva manner as to extenddiametrically across the' base of the fuse plug,'toma'kea contact vwiththe ferrule' 5, 'and the` plug then screwed home, it will -be foundthatifthe wire is heavy enough to'resist the mutilating elfe-ct of thecomplement-ary corrugatedv parts of the plug and adapter, the lower endof the contact reach the head 12 of the contact screw, and the circuitwill not be closed Iftinfoil, or v'very light wire is laid from ythehead 12 of the contact screw, to ferrule, turning effect of the plug asit is screwed to its seat, and the shearing effect of thecomplementarycorrugations of the plug and adapter, will shear and mutilate the wireor tinfoil completely. 'If the wire or tinfoil is fine, or thin enoughtoconform to the shape vof the complementary corrug-ations of the plug andadapter, it will be partially sheared, and so mutilated, that it willnot have al current carrying capacity of over the fifteen amperes, theusual safe carryl ing capacity of the electrical system, and in thiscase will not injure thesame.

I claim:

v1. In a safety fuse device, a fuse block having a feeder connection,and a branch circuit connection, a ferrule mounted in the block, anadapter having a perforated center, a concentric recess formed in theupper faceof the adapter, and va peripheral recess formed in theadapter, a spring locking wire adapted'to fit in the peripheral recess,and lock the adapter within the ferrule, a fuse plug having a centrallydisposed contact pin'therein, a fuse A plug'disc having a concentricprojecting ring thereon formed complementary to the concentric adapterrecess, a Contact screw mounted in the fuse block, means connecting nthe contact screwl with the feeder connection, and means connecting. theYcontact pin with the branch circuit connection;

2. In a safety fuse device, an adapter hav'- T adapter, a` spring ringmounted. in the Vpe-Z.

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ripheral groove, and means for holding the spring ring within theperipheral limits of the adapter.

3. In a safety fuse device, an adapter halving a central perforationtherein, a concentric recess in its upper surface, a recess in itsbottom face, a peripheral groove formed on the outer Walls of the adater, a spring ring mounted in the groove, a use plug having a cent-ralcontact in, adapted to pass through the central per oration of theadapter, and a concentric projecting ring on the bottom of the fuse lugformed complementary to the concentrlc recess of the adapter.

4. In a safety fuse device, a ferrule, having a number of screw threadsformed therein, an adapter having a peripheral groove and a pair ofalined holes therethrough, a

split spring ring having tapered overlap- Y ping ends, and a pair ofalineable holes therethrough mounted in the groove, and holding andreleasing means comprising a holding pin adapted to pass through theholes in the adapter and split ring for holding the spring ring Withinthe periphery7 of the adapter while the same is being mounted in theferrule, and for releasing the ends of said ring when the latter is indesired position Within the ferrule.

5. In a safety fuse device, a fuse block having incoming and out-goingelectrical circuit connections, a contact screw having connections Withthe incoming electric circuit connection, an adapter having a centralperforation therethrough, a concentric recess in the upper face of theadapter, a recess in the adapter for accommodating the head of thecontact screw, a ferrule on the use block having threads formed therein,a fuse plug having a contact pin mounted therein, a disc on the base ofthe fuse plug having a concentric projection thereon, formedcomplementary to the concentric recess of the adapter, for permittingthe contact pin to form an electrical connection with the cont-actscrew, means for locking the adapter in the ferrule grooves, and meansconnecting the contact pin with the out-going circuit connection.

6. In a safety fuse device, a split spring ring, having tapered ends,adapted to slide upon each other, and having erforations in said endsadapted to be in a ignment when the spring is in a contracted position,and a holding pin adapted to pass through the perforations, and hold thespring in contracted position.

7. In a safety fuse device, an adapter, having a peripheral recessformed therein, and a pair of perforations yin alignment with eachother, a split spring ring, having a pair of perforations therein whichcan be aligned with each other and the perforations in the adapter whenthe spring ring is in a contracted position, and a pin adapted to pass

